Structural, magnetic and Mössbauer spectroscopy characterisation of the Fe-15 wt %Si nanocrystalline powder obtained by mechanical alloying and annealing

Abstract

Fe-Si alloy with a large content of 15 wt % Si has been obtained in nanocrystalline state by mechanical alloying. The influence of the milling duration and heat treatment on the formation of the alloy, its structure and magnetic properties was investigated. The Fe-Si alloy is obtained after 4 hours of mechanical alloying as shown by X-ray diffraction measurements. Annealing of the as-milled powders leads to the formation of the Fe3Si intermetallic compound with a DO3-type superstructure. The progressive formation of the Fe-Si alloy during mechanical alloying and annealing was investigated by 57Fe Mössbauer spectrometry. Thermal stability of the Fe-15 wt % Si powders was studied by differential scanning calorimetry (DSC). The alloy formation is also shown by the decrease of the saturation magnetisation in the first hours of mechanical milling. A difference in the saturation magnetisation of the as-milled and the milled and subsequently annealed samples is due to the magnetic moment of the iron atoms which is different in the Fe3Si structure. The Curie temperature decreases during the formation of the Fe-Si alloy.